The health status of laboratory animals may significantly influence the outcome of experimental procedures. It is generally accepted that the target microbiological status is that specified within the FELASA Recommendations (FELASA, 2002). In this way, the reporting of microbiological status is standardised allowing animals to be exchanged between laboratories and breeders in the confidence that known microbial adventitious agents will not be inadvertently introduced.

Development and maintenance of genetically altered animals under such stringent microbiological conditions may be complex and may require a highly controlled environment, which is expensive to maintain. The introduction of a new line into such an environment demands strict precautions in order to avoid the entry of pathogens into the facility.

Embryo transfer is a reliable method of introducing new lines into an animal facility based on the experience that embryos in the uterus are in a pathogen free environment. Animals (heterozgotes or homozygotes) are received into our Quarantine area and are mated according to your instructions. Pre-implanted embryos are removed, washed in sterile medium and transferred into the uterus of an adventitious-pathogen-free pseudo-pregnant female. The resulting pups are, therefore, free from pathogenic organisms at birth. Subsequent microbiological monitoring of the pups and/or foster mothers is carried out to verify the status. The resulting animals are returned to you at approximately 6 weeks of age.